It just started tonight, what sounds like a low pitch whine {almost like a big pusher pump IE:Aeromotive} that goes up and down in pitch, depending on throttle postion with accleration at very low speeds like right off idle to 10 mph. . i don't know for sure but was thinking power steering pump, what else?It doesn't change pitch when i move the steering wheel back and forth like a P/S pump should. . 
